Thanks for your answer.

>Your assumption is incorrect. As the latitude changes, so does the
>number of pixels per degree.

Does this means that for a fixed tile height of 256 pixels, the number of
degrees is different at 60 deg. latitude thant to 40 deg. latitude ?


My idea was to create an X/Y coordinate system based on degrees (not pixels)
with (0,0) at the center, then I was thinking in to calculate the tile
number for a given X/Y or (long/lat) point by simply doing something like (I
need this for some kind of desktop drawing program) :

tileleft = ( X - XOrigin) / tile_width_degrees
tiletop = (Y - YOrgin) / tile_height_degrees


Just to be sure, I must ask: then, based on your answer and what I have seen
in your page, it is not possible to do so ?


Thanks


2010/5/11 maps.huge.info [Maps API Guru] <[email protected]>

> Your assumption is incorrect. As the latitude changes, so does the
> number of pixels per degree.
>
> I suggest reviewing the formulas for computing tiles and pixels, they
> are fairly simple but are not linear.
>
> You can get them from my perl module here:
>
> http://www.usnaviguide.com/google-tiles.htm
>
> -John Coryat
>
> http://maps.huge.info
>
> http://www.usnaviguide.com
>
> http://www.zipmaps.net
>
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